Salmonella Cases Up, E. Coli Down in U.S.

The rate of Salmonella infection in the U.S. held steady from 1996 to 2006, but has spiked by 15% since then, CDC researchers reported.

Conversely, illnesses linked to Shiga toxin-producing Escherichia coli (STEC) O157 have decreased by nearly half in the last 15 years.

Of the 19,089 infections, 4,247 hospitalizations, and 68 deaths from foodborne pathogens in 2010, Salmonella infection was the most common, accounting for 2,290 hospitalizations and 29 deaths, according to a study published online Tuesday in Morbidity and Mortality Weekly Report.

STEC O157 infection caused 0.9 illnesses per 100,000 in 2010, compared with two cases per 100,000 in the 1996-1998 reporting period.

The CDC credits the reduction in E. coli to improved detection and investigation of outbreaks with the following:

The CDC's PulseNet surveillance system

Cleaner slaughter methods

Testing of ground beef for E. coli

Better inspections of ground beef processing plants

Regulatory improvements, such as the prohibition of STEC O157 in ground beef, resulting in beef recalls

Also, there is an increased awareness by consumers and restaurant employees of the importance of properly cooking beef, according to Thomas R. Frieden, MD, MPH, Director of the CDC, who spoke during a press briefing.

Salmonella, which is responsible for an estimated $365 million in direct medical costs each year in the U.S., can be challenging to address because so many different foods, like meats, eggs, produce, and even processed foods, can become contaminated with it. Finding the source can be challenging because it can be introduced in many different ways, Frieden said.

Under the recently enacted Food Safety Modernization Act, however, the FDA has implemented new egg safety requirements, which are expected to reduce illnesses caused by Salmonella by 60%, said Michael R. Taylor, FDA Deputy Commissioner for Foods, during the press briefing.

"The U.S. Department of Agriculture has been tightening standards aimed at preventing Salmonella infection, and, in July 2011, will reduce the allowable contamination of whole broiler chickens at processing plants from 20% to 7.5% of carcasses," according to the report.

In addition to the reduction in E. coli, the overall incidence of infection with six key pathogens in 2010 was 23% lower compared with 1996-1998, according to the MMWR study.

The data in the MMWR study come from FoodNet, a collaborative program among the CDC, 10 state health departments, the U.S. Department of Agriculture's Food Safety and Inspection Service, and the FDA.

The surveillance area includes approximately 15% of the U.S. population. However, the CDC estimates that there are 29 infections for every lab-confirmed Salmonella infection.

"The estimated total number of Salmonella infections is 1.2 million per year," said Chris Braden, MD, Director of Foodborne, Waterborne and Environmental Diseases at the CDC, during a press briefing.

The report showed that children under 5 years were hit the hardest in 2010 by all pathogens except Vibrio and Cyclospora. The incidence rate for Salmonella, for example, was 69.5 per 100,000 compared with 21.4 for those between 5 and 9 years and 17.0 for those over 60.

The second most common infection for children under 5 was from Campylobacter, with an incidence rate of 24.4 per 100,000 compared with 13.9 for those over 60.

While this report is not related to the recent outbreak in Europe of STEC O104, concerns have been raised in the U.S. about food safety.

Four people in the U.S. who had recently traveled to Germany are being evaluated for possible STEC O104 infection. Tests of the four U.S. cases are still being analyzed.

"We have not identified any spread of STEC O104 from these four cases nor have we identified anyone else in the U.S. who has potentially become ill from contaminated products," said Frieden.

Testing for STEC contamination carries a heavier price tag than testing for more common food pathogens, Braden said. Many state and local facilities have not been willing or able to absorb the additional cost as they contend with cutbacks in staff and financial resources, he said.

Salmonella has more than 2,500 serotypes, but the three most common reported subtypes in 2010 are Enteritidis (22% of all cases), Newport (14%), and Typhimurium (13%).

Compared with 1996–1998, the incidence in 2010 of Typhimurium significantly decreased by 53% (CI 46% to 58%), while that for Newport and Enteritidis increased by 116% (CI 67% to 180%) and 76% (CI 45% to 113%), respectively.

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